Using dissolved noble gas and isotopic tracers to evaluate the vulnerability of groundwater resources in a small, high elevation catchment to predicted climate changes

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We use noble gas concentrations and multiple isotopic tracers in groundwater and stream water in a small high elevation catchment to provide a snapshot of temperature, altitude, and physical processes at the time of recharge; and to determine subsurface residence times of different groundwater components. They identify three sources that contribute to groundwater flow: (1) seasonal groundwater recharge with short travel times, (2) water from bedrock aquifers that have elevated radiogenic {sup 4}He, and (3) upwelling of deep fluids that have 'mantle' helium and hydrothermal carbon isotope signatures. Although a bimodal distribution in apparent groundwater age indicates that groundwater storage ... continued below

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Singleton, M J & Moran, J E October 2, 2009.

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We use noble gas concentrations and multiple isotopic tracers in groundwater and stream water in a small high elevation catchment to provide a snapshot of temperature, altitude, and physical processes at the time of recharge; and to determine subsurface residence times of different groundwater components. They identify three sources that contribute to groundwater flow: (1) seasonal groundwater recharge with short travel times, (2) water from bedrock aquifers that have elevated radiogenic {sup 4}He, and (3) upwelling of deep fluids that have 'mantle' helium and hydrothermal carbon isotope signatures. Although a bimodal distribution in apparent groundwater age indicates that groundwater storage times range from less than a year to several decades, water that recharges seasonally is the largest likely contributor to stream baseflow. Under climate change scnearios with earlier snowmelt, the groundwater that moves through the alluvial aquifer seasonally will be depleted earlier, providing less baseflow and possible extreme low flows in the creek during summer and fall. Dissolved noble gas measurements indciate recharge temperatures are 5 to 11 degrees higher than would be expected for direct influx of snowmelt, and that excess air concentrations are lower than would be expected for recharge through bedrock fractures. Instead, recharge likely occurs over diffuse vegetated areas, as indicated by {delta}{sup 13}C-DIC values that are consistent with incorporation of CO{sub 2} from soil respiration. Recharge temperatures are close to or slightly higher than mean annual air temperature, and are consistent with recharge during May and June, when snowpack melting occurs.

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PDF-file: 41 pages; size: 2.3 Mbytes

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  • Journal Name: Water Resources Research, vol. 46, n/a, December 14, 2010, W00F06; Journal Volume: 46

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  • Report No.: LLNL-JRNL-418084
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 1020335
  • Archival Resource Key: ark:/67531/metadc846777

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  • October 2, 2009

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  • May 19, 2016, 3:16 p.m.

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  • Dec. 2, 2016, 5:58 p.m.

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Singleton, M J & Moran, J E. Using dissolved noble gas and isotopic tracers to evaluate the vulnerability of groundwater resources in a small, high elevation catchment to predicted climate changes, article, October 2, 2009; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc846777/: accessed September 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.